An engine may be supplied different types of fuel during different engine operating conditions to enhance engine performance and/or fuel economy. For example, an engine may be supplied gasoline via a first fuel injector and ethanol via a second fuel injector. The two fuels may be supplied from a fuel mixture that is separated into two fuels or via filling different fuel tanks with different fuels.
United States of America Patent Publication 2008/000633 describes systems to handle fuel tank vapors for multiple fuel tanks. However, in the systems described by publication 2008/000633 fuel vapors of higher octane fuels may condense in fuel tanks holding or storing lower octane fuel, and vice versa. Consequently, the higher octane fuel may not be best utilized, or alternatively, the higher octane fuel may have to be separated from the lower octane fuel so that it may be utilized. However, parasitic losses may increase due to energy being lost from separating the higher octane fuel from the lower octane fuel.
The inventors herein have recognized the above-mentioned disadvantages and have developed a fuel storage system, comprising: a first fuel tank; a second fuel tank; a first fuel vapor storage canister; a second fuel vapor storage canister; a first conduit coupled to the first fuel tank and the first fuel vapor storage canister; a second conduit not coupled to the first conduit, the second conduit coupled to the first fuel tank and the second fuel vapor storage canister; and a valve positioned along the second conduit.
By not allowing fluidic communication between fuel tank vapor paths, it may be possible to prevent higher octane fuel vapors from condensing and mixing with lower octane fuel in a fuel tank storing lower octane fuel. Further, fuel tank vapor paths may be constructed such that fuel vapors originating from fuel tanks storing fuel having a lower octane number may be directed to a fuel tank storing fuel having a higher octane number. In this way, high octane fuel vapors that were produced via diurnal fuel system heating may be captured in a fuel tank storing a fuel having a higher octane number so that higher octane fuel vapors may condense into a higher octane liquid fuel. Additionally, parasitic losses associated with separating higher octane fuel from a lower octane fuel mixture may be reduced by taking advantage of diurnal heating so that separating higher octane fuel from a lower octane fuel mixture may not require engine work.
The present description may provide several advantages. In particular, the systems described may reduce parasitic engine losses that decrease engine fuel economy. Additionally, the systems may provide for more efficient use of fuel vapors. Further still, the systems described may be applied to systems that include more than two fuel tanks and two types of fuel.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.